Personal audio devices, including wireless telephones, such as mobile/cellular telephones, cordless telephones, mp3 players, and other consumer audio devices, are in widespread use. Such personal audio devices may include circuitry for driving a pair of headphones or one or more speakers. Such circuitry often includes a power amplifier for driving an audio output signal to headphones or speakers.
One particular characteristic of a personal audio device which may affect its marketability and desirability is the dynamic range of its audio output signal. Stated simply, the dynamic range is the ratio between the largest and smallest values of the audio output signal. One way to increase dynamic range is through the use of a multipath analog-to-digital subsystem comprising a plurality of parallel analog-to-digital converters (ADCs). Multipath circuits including multiple parallel ADCs may reduce noise as one path may be optimized for processing small amplitude signals (e.g., for processing low noise signals) while another circuit path may be optimized for large amplitude signals (e.g., allowing for higher dynamic range). Examples of such multipath circuits are disclosed in U.S. Pat. No. 9,071,267 (the “Schneider Reference”), which is incorporated herein by reference.
Another way to increase dynamic range is through the use of signal magnitude-dependent digital gain and a corresponding analog attenuation applied to a digital-to-analog conversion subsystem comprising a digital-to-analog conversion subsystem having a digital gain and an output amplifier having an analog gain (or attenuation). Such a digital-to-analog conversion subsystem may enhance dynamic range as compared to approaches in which the digital gain and analog attenuation are static, as it may reduce the noise injected into audio output signal VOUT, which noise may be a generally monotonically increasing function of the gain/attenuation of the output amplifier. Examples of such digital-to-analog conversion subsystems are disclosed in U.S. patent application Ser. No. 14/083,972 (the “Satoskar Reference”), which is incorporated herein by reference.